# Single-Qubit Quantum Gates on a Bloch Sphere

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Using the Bloch sphere, a cubit can be represented as a unit vector (shown in red) from the origin to the point on the unit sphere with spherical coordinates . A single-qubit quantum gate operating on produces a rotated qubit , represented by the green vector. Check the box for "add gate 2?" to perform a second operation using gate . This produces another qubit , which is represented by the blue vector. You can choose from the gates H, X, Y, Z, S and T as defined in the Details.

Contributed by: S. M. Blinder (August 2017)

Open content licensed under CC BY-NC-SA

## Snapshots

## Details

The action of the single-qubit quantum gates can be represented by unitary matrices acting on the qubit

:

Hadamard gate: TextData[""]=(111-1),

Pauli X gate: InlineMath=(0110),

Pauli Y gate: TextData[""]=(0-ii0),

Pauli Z gate: InlineMath=(100-1),

phase (or gate: InlineMath=(100i),

gate: InlineMath=(100ei π4).

In general, the operation InlineMath (αβ) gives a qubit of the form

,

with an overall phase factor of no physical significance. Multiplication by removes this factor and reduces the qubit to the canonical form

.

References

[1] M. A. Nielsen and I. L. Chuang, *Quantum Computation and Quantum Information: 10th Anniversary Edition*, Cambridge: Cambridge University Press, 2010.

[2] G. Fano and S. M. Blinder, *Twenty-First Century Quantum Mechanics: Hilbert Space to Quantum Computers*, Berlin: Springer, 2017.

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